Vibrator motors are available in a variety of configurations. Typically, the motor includes a stack of stationary laminations secured inside a case for a hair clipper or other device. A coil wrapped around the stationary laminations produces varying electromagnetic fields that drive a complimentary set of moving laminations.
The moving laminations are typically secured in an appropriate location with respect to the stationary laminations using a spring-like tail bracket. At least one, and usually two or three, pole faces are formed where the stationary and moving laminations are close to each other. One end of the tail bracket is secured to an end of the moving laminations, and the other end of the tail bracket is secured to the housing or the stationary laminations. The tail bracket/moving laminations assembly forms an arm of sorts that is attached at one end and open at the other. The open end of the moving laminations reciprocates to drive a clipper blade or some other device.
In addition to the tail bracket, conventional vibrator motors also have a mechanical spring system that allows the motor to be tuned to a proper resonant frequency so that it operates properly. The spring system also determines the position of the moving laminations and clipper blades when the coil is not energized. A typical spring system has two coil springs. When the coil is energized by alternating current, the tail bracket, the spring system and the electromagnetic fields generated by the coil make the clipper blade or other device reciprocate. Motor tuning is accomplished by adjusting the stiffness of the springs in the spring system to obtain good performance, usually by turning an appropriate screw which adjusts the tension in the springs. If not properly tuned the motor will not have sufficient power, or it will flutter or clatter and essentially operate in an uncontrolled manner or not operate at all.
Many things affect tuning, including the weight of the moving parts, the weight of the stationary parts, the length of the moving part of the arm, the energy release rate of the tuning springs, the alignment of the pole faces, the stiffness of the tail bracket, and other factors. Variations in any of these aspects of the device can cause problems in operation, and problems in manufacturing and assembly.
Variations in the tail bracket present particularly difficult manufacturing challenges. If the tail bracket material thickness or hardness varies even slightly, the resonant frequency (the speed at which the arm vibrates naturally) is affected, since the force required to move the arm is related to the stiffness of the tail bracket. Even variations in bends in the tail bracket can cause assembly problems, because they can make the motor untunable.
The tail bracket acts as a secondary tuning spring in addition to the two coil type tuning springs. If the neutral unsprung position of the tail bracket in the assembly is not the same as the neutral position of the arm when the clipper has been tuned, the tail bracket works against one of the tuning springs, applying a heavier load to one of the tuning springs than to the other. This causes the resonant frequency to change, since the spring load changes in order to compensate for the bias load applied by the tail bracket. Moreover, the force required to move the arm also varies under these conditions. Variations in tail bracket bends also affect the orientation of the blades, and in some cases make it difficult to properly align the blades of hair clippers.
Another problem with known vibrator motors is that they require several pieces that must be assembled together in the case. The case is usually molded from plastic, which can have substantial dimensional variation due to warping and dimensional variation inherent in the molding process. These variations can create manufacturing and assembly problems.
Dimensional variations of the pieces assembled in the case can create additional manufacturing and assembly problems. For example, if the drive finger is the wrong length, it can cause tuning problems due to the change in resonant frequency caused by a change in the length of the arm. In hair clippers, a drive finger that is too long can make it impossible to align the tips of the bottom blade teeth with the tips of the top blade teeth so that they have the correct overlap distance. If the drive finger is crooked, it can cause a crooked appearance of the top blade. If the drive finger is too far to the right or left, the teeth of the bottom blade might not be able to be adjusted to line up with the top blade teeth, causing a loss of cutting performance.
Dimensional variations can also cause misalignment of the pole faces of the stationary and moving laminations. If there is excessive variation in the case, and/or in the arm assembly, the pole faces of the arm laminations will not be aligned with the pole faces of the coil laminations. There can be a vertical misalignment or the laminations can be twisted such that there may be a larger gap between poles near the top than at the bottom, or vice versa. Also, one of the poles may be closer together than the other poles. In any of these cases, the motor will not operate as efficiently as if the poles were well aligned, because the magnetic gap will be larger than it should be at some place, resulting in loss of power and/or efficiency or higher than normal power consumption.
These problems can occur when one part, such as the case, is out of tolerance, or when the parts are individually within acceptable tolerances, but the cumulative variations from desired specifications is unacceptably high. Tolerance accumulation problems are often difficult to identify and resolve, particularly where the number of parts is high.
In some conventional motors, the tuning springs are located at the rear or bottom of the motor, away from the drive end of the arm. This can also cause tuning problems, because the springs have poor leverage.
In all, conventional motors have a relatively high number of parts which make them expensive and difficult to manufacture and assemble. Automation is also difficult because the designs are fairly complicated. Accordingly, there is a need for vibrator motors that are easier to manufacture and assemble, and are more adaptable to automated manufacture and assembly.
Accordingly, one object of this invention is to provide new and improved vibrator motors.
Another object is to provide new and improved vibrator motors for hair clippers and the like.
Another object is to provide new and improved vibrator motors that are less expensive and easier to manufacture and assemble than conventional motors.
Yet another object is to provide new and improved vibrator motors that do not have a tail bracket or the problems associated with tail brackets just discussed. A still further object is to provide new and improved vibrator motors that are less susceptible to parts tolerance build-up.
Still another object is to provide new and improved vibrator motors having fewer parts than conventional motors.
Still another object is to provide new and improved vibrator motors that can be pre-assembled and installed in a case after assembly.